Our next step was to analyze overall survival (OS) by Kaplan–Meier and Cox regression both for the basic TCGA glioma cohorts («astrocytoma», «oligoastrocytoma», «oligodendroglioma», «glioblastoma») and for the revised cohorts formed in accordance with the WHO CNS5 classification («astrocytoma, IDH-mutant», «oligodendroglioma, IDH-mutant, and 1p/19q-codeleted», «glioblastoma, IDH-wildtype»). This evidence concerns the gene IDH1 and oligoastrocytoma.